{
\def\sym#1{\ifmmode^{#1}\else\(^{#1}\)\fi}
\begin{tabular}{l*{3}{c}}
\hline\hline
                    &\multicolumn{1}{c}{\specialcell{\;\;\;\;\;\; Fecal \\ contamination }}&\multicolumn{1}{c}{\specialcell{\;\;\;\; Arsenic \\ contamination \\ \;\;\;\; (WHO \\ \;\;\;\; threshold) }}&\multicolumn{1}{c}{\specialcell{\;\;\;\; Arsenic \\ contamination \\ \;\;\;\;\; (Bangladeshi \\ \;\;\;\;  threshold) }}\\\cmidrule(lr){2-2}\cmidrule(lr){3-3}\cmidrule(lr){4-4}
                    &\multicolumn{1}{c}{(1)}   &\multicolumn{1}{c}{(2)}   &\multicolumn{1}{c}{(3)}   \\
\hline
Difference          &       -0.13***&       -0.58***&       -0.35***\\
                    &      (0.05)   &      (0.04)   &      (0.03)   \\
\hline
Mean (project TW)   &        0.34   &        0.06   &        0.01   \\
Mean (other TWs)    &        0.46   &        0.63   &        0.34   \\
N                   &        3399   &        3515   &        3515   \\
\hline\hline
\end{tabular}
}
